Plasticized PVC composition

ABSTRACT

The invention developed compositions of plasticizers obtained from the partial transesterification, acetylation and epoxidation of vegetable oils with ethanol or glycerin, henceforth called partially transesterified epoxidized bioesters.

The present descriptive report refers to a patent of invention ofprimary PVC plasticizers composed of epoxidized bioesters of vegetableoil fatty acids obtained by partial transesterification of vegetableoils with ethanol or glycerin and further acetylation and epoxidation,and plasticized PVC composition with epoxidized bioesters resulting frompartial transesterification, acetylation and epoxidation, belonging tothe technical field of polymer additives that were developed to improvethe properties of PVC resin-based polymers, in addition to providing alower cost for renewable compounds, such as those obtained with the useof vegetable oils.

Polyvinyl chloride (PVC) is a polymer well known for its wide range ofindustrial applications, but it presents natural rigidity due to itsmolecular structure, requiring the use of some additives to increase itsrange of useful applications, resulting in compositions that arecommonly known as PVC compounds.

Among known compounds, plasticized PVC compounds present highflexibility and are used in films, wire and cable insulation, packaging,hoses, toys, etc. Plasticized PVC compounds are obtained by theaddition, in different levels, of additives known as plasticizers, toprovide the desired flexibility.

Plasticizers are, in general, high boiling point liquids with averagemolecular weight between 300 and 600, linear or cyclic carbon chains (14to 40 carbons) that, when added to the PVC resin allow for movementbetween the PVC molecules promoting flexibility to the final compound.

Currently, primary plasticizers used in the industry are mainlyphthalates, obtained from petroleum and, in addition to being dependenton the fluctuations of petroleum prices, phthalates are suspect ofhaving adverse effects on human health.

As a result, a search was initiated to find alternatives that aretechnically and economically viable to replace petroleum basedplasticizers. Epoxidized soybean oil was proposed as a primaryplasticizer, however, its low compatibility with PVC limited its use tosmall quantities, keeping it from completely replacing phthalates as aprimary plasticizer.

Another proposition was the use of epoxidized linseed oil, that in spiteof having a similar molecular weight to soybean oil presents a higheroxirane index (8 to 12) and thus greater compatibility with PVC.However, its use is severely restricted due to its higher price.

As such, it was studied the processes of transesterification orinteresterification of vegetable oils combined with epoxidation, asprimary plasticizers for PVC. Patent GB934689 describes the preparationof vegetable oils with high linolenic acid contents (such as linseedoil), presenting high iodine index (175 to 200) and high oxirane index(8,5 to 12,33), that are transesterified with lower alcohols (methanol)and subsequently epoxidized. U.S. Pat. No. 4,421,886 and U.S. Pat. No.5,886,072 propose the use of esters of soybean oil transesterified withpentaeritritol, whereas the latter patent proposes the use of theseesters in a mixture with other plasticizers. U.S. Pat. No. 4,605,694describes the use of trimelitic acid and pentaeritritol esters, whilethe U.S. Pat. No. 5,430,108 proposes the use of esters of pentaeritritolwith alcanoic acid. Finally, the Brazilian patent application BR0111905-2 describes the use of soybean oil transesterified withmethanol, ethylene glycol, propylene glycol, pentaeritritol, saccharose,and interesterified linseed oil.

Some of these esters (obtained from pentaeritritol, trimelitic acid,ethylene glycol, propylene glycol and interesterified linseed oil) asplasticizers present the drawback of having larger molecular weight andmuch higher cost when compared to phthalates. Others obtained frommethanol, still have a price dependency on petroleum. Additionally, theproposed esters are composed by mixtures of esters with oxirane indexesgreater than 8. Finally, with exception of the methanol esters, theother types of esters have been used as primary plasticizers for PVConly in laboratory tests, indicating the difficulty in obtaining anadditive that is both technically and economically viable.

Therefore, the objective of the present invention is to obtaintechnically and economically viable alternatives of primary plasticizersfor PVC compounds derived exclusively from renewable sources (vegetableoils and sugar cane ethanol) that are completely compatible with the PVCresin.

With the purpose of overcoming the aforementioned problems and complyingwith the objectives previously described, the invention developedcompositions of plasticizers obtained from the partialtransesterification, acetylation and epoxidation of vegetable oils withethanol or glycerin, henceforth called partially transesterifiedepoxidized bioesters. This invention differs from the state of the artby providing partially transesterified, acetylated and epoxidizedbioester plasticizers composed of a mixture of mono, di andtriglycerides and esters of vegetable oils fatty acids, presenting lowlinolenic acid content and oxirane indexes below 8.

Vegetable oils are composed by triglycerides that contain glycerinmolecules attached to three saturated, mono-unsaturated, di-unsaturatedand tri-unsaturated fatty acids such as palmitic, oleic, linoleic, andlinolenic acids, among others. These fatty acids vary also in regards tothe size of the carbon chain, presenting 14 to 18 carbon atoms for theoils referred in this invention.

The partial transesterification reaction of vegetable oils is employedto partly separate some of the fatty acids from the glycerin moleculeand bond them to other alcohol molecules, resulting in a mixture ofmono, di and triglycerides and esters of the partly transesterifiedvegetable oil. Such mixture presents superior properties when comparedto those of the triglyceride. This wide range of ester varietiesincreases the possibilities of compatibility with PVC, in addition toallowing different properties in the plasticized PVC.

It is important to note that the current state of the art for theproduction of modified vegetable oils for PVC plasticizing as well asother applications, such as biodiesel, only mentions completetransesterification reactions, as partial reactions are not welcome andeven detrimental to the production of such products as they are producedtoday.

The wide variety of bioesters obtained in the present inventionincreases the compatibility with the PVC resin, in addition to providedifferent properties to the plasticized PVC.

The partial transesterification reaction results mostly in the randomsubstitution of the fatty acids of the vegetable oil molecule by one ortwo hydroxyl (OH) radicals, introducing one or two points of thermalinstability in the resulting molecule. In order to correct for that andto provide the product with suitable chemical and physicalcharacteristics to be used as a PVC plasticizer, the removal of such OHradicals is necessary.

Such elimination of the hydroxyl radical is carried through a processcalled acetylation, where the mono and diglyceride molecules are reactedwith acetic acid, creating a short ramification with 2 carbon atoms. Theacetylation reaction eliminates the OH radical in the molecules, andeliminates the thermal stability problem.

Finally, the epoxidation process introduces an atom of oxygen in thedouble bonds of the fatty acid carbon chains, forming an oxirane ringthat makes the ester more polar and thus more compatible with the PVCresin. The greater the number of double bonds in the original ester, thegreater the number of oxirane rings formed, and therefore increasedcompatibility with PVC. In addition, the substitution of the doublebonds by the oxirane ring in the fatty acid chains increases thechemical and thermal stability of the resulting molecule.

The compatibility of the epoxidized bioesters with the PVC resin dependson the unsaturation of the original esters and the level of epoxidationof the double bonds. The bioesters of this invention presentcompatibility with PVC even when the resulting oxirane index is below 8,which is not foreseen in the current state of the art.

In a preferred embodiment the bioesters are obtained by the partialtransesterification of a mixture of vegetable oils or one vegetable oil,such as soybean oil, with ethanol in a smaller proportion vegetable oil:alcohol than that used for a complete transesterification reaction.After obtained, the mixture of mono and diglycerides resulting from thepartial reaction are acetylated with acetic acid to reduce or eliminatethe hydroxyl radicals. The mixture of acetylated mono and diglycerides,as well as the triglycerides and esters of the vegetable oil fatty acidsare then epoxidized. The vegetable oils are chosen among the oils withan iodine index between 120 and 170, such as soybean oil, corn oil,linseed oil, sunflower oil, or a mixture of them.

The plasticizer composition obtained by the partial transesterificationof vegetable oils with ethanol, acetylation and epoxidation presents amixture of the following molecules:

With R preferably selected randomly from the epoxidized oleic, linoleicand linolenic acids.

The variation of reaction parameters such as catalyst amount,temperature, reaction time and oil: alcohol molar proportion allows fora wide range of possible compositions in the final mixture to obtain aproduct that best suits the desired application.

In a preferred embodiment the partial transesterification reaction isobtained by the use of 50% of the amount of catalyst for a completereaction as well as a molar proportion of soybean oil: ethanol of 1:10and 1:20. After obtained, the mono and diglycerides are reacted withacetic acid in the presence of pyridine to replace the hydroxyl radicalsby acetic terminations. The mixture of acetylated mono and diglyceridesand esters of the vegetable oil fatty acids are then epoxidized, in areaction where the double bonds in the fatty acid chains react with insitu free oxygen obtained from high concentration peroxides, which undercertain conditions of temperature and stirring form the oxirane rings.In this embodiment the product obtained had 10% of epoxidizedtriglycerides, 50% of epoxidized ethyl soyate and 40% of acetylated andepoxidized mono and diglycerides.

The final product obtained is a viscous transparent liquid slightlyyellow and with a faint odor similar in characteristic to the originalsoybean oil used, presents an oxirane index between 4 and 8, long linearmolecular chain (between 20 to 41 carbon atoms) and medium averagemolecular weight (between 450 and 500) when compared to the epoxidizedsoybean oil.

In another embodiment the plasticizers are obtained by the partialtransesterification of a mixture of vegetable oils or one vegetable oil,such as soybean oil, with glycerin, under similar reaction conditions asthose presented above. The vegetable oils are chosen among the oils withan iodine index between 120 and 170, such as soybean oil, corn oil,linseed oil, sunflower oil, or a mixture of them.

The composition of the plasticizer obtained by the partialtransesterification of vegetable oils with glycerin and subsequentacetylation and epoxidation presents a mixture of the followingmolecules:

With R preferably selected randomly from the epoxidized oleic, linoleicand linolenic acids.

It is important to note that the glycerin used in this process isobtained from the very same reaction of complete transesterification ofvegetable oils with alcohols and described in various processes, andtherefore is also renewable.

In a preferred embodiment the soybean oil is reacted with pure glycerinin 1:0.2 to 1:0.4 soybean oil: glycerin proportions, at room pressureand temperatures between 170° C. e 220° C., using alkyl benzenesulfonate as catalyst, sodium ethylate or soda, resulting in a mixtureof mono and triglycerides and at least 50% of diglycerides with fattyacid chains in the extremes of the glycerin molecule and the hydroxylradical (OH) in the middle. This mixture is then acetylated andepoxidized according to the procedures indicated above.

Even though plasticizers obtained present acetylated epoxidizeddiglyceride of at least 50%, the final product obtained is a viscoustransparent liquid slightly yellow and with a faint odor similar incharacteristic to the original soybean oil used. Presenting an oxiraneindex between 4 and 8, long linear molecular chain with average 41carbon atoms and medium to high average molecular weight (700) whencompared to the epoxidized soybean oil (900).

In another embodiment, plasticized PVC is obtained by mixing i) 100parts (weight/weight) of at least one type of PVC resin; ii) 1 to 200parts (weight/weight) of plasticizer, which consists of epoxidizedbioesters with an oxirane index below 8; the mixture is then homogenizedand later extruded.

In a preferred embodiment the plasticizer is made from a fatty acidesters and glyceryl esters, derived from vegetable oil, partiallytransesterified with ethanol, which mono and diglycerides are acetylatedand then, along the ethyl esters and triglycerides, are epoxidized. Suchmixture is denominated epoxidized ethyl soyate and epoxidized mono, diand triglyceride soyates.

In another preferred embodiment the plasticizer is made from a mixtureof partially transesterified mono, di and triglycerides of soybean oilacetylated and epoxidized, such mixture denominated epoxidized mono, diand triglyceride soyates, with at least 50% of epoxidized diglyceridesoyate.

The plasticized PVC is therefore free of phthalate plasticizers. It isimportant to point out that the plasticizers composed of epoxidizedbioesters of ethanol and/or epoxidized glycerides provide some propertyimprovements to the plasticized PVC, improvements not foreseen in thestate of the art, such as greater flexibility, greater resistance to UVlight degradation, better physical properties at low temperatures,better mixture efficiency (salvation) of the PVC resin and betterresistance to aliphatic solvents extraction.

PVC compounds plasticized with the objects of this invention presentsuperiority in all these properties when compared to plasticized PVCprepared with plasticizers revealed by the state of the art whilekeeping the same proportion of plasticizer/PVC resin.

Therefore, the plasticizers of this invention work out theinconveniences described in the state of the art, presenting thefollowing additional advantages:

1. Can be produced from natural, renewable and economically viablesources (sugar cane and soybean oil), in addition to being adequate tohuman contact;

2. Are totally compatible with the PVC resin, when compared to theepoxidized soybean oil and can be used as primary plasticizers;

3. Present less odor and coloration when compared to the epoxidizedsoybean oil;

4. Present competitive costs when compared to all primary plasticizersand significantly lower costs when compared to the current alternativesto replace phthalates (trimelitates, citrates, polymerics) and lowercosts when compared to most of the alternatives present in the state ofthe art, which use more expensive alcohols or acids;

5. Provide better salvation and plasticization efficiency in the PVCcompound when compared to the current primary plasticizers alternativesor the majority of the developments of the state of the art, producinglighter and more flexible compounds with less plasticizers;

6. Aid in the thermal stabilization of PVC, allowing more processingtolerance or cost reduction of the stabilizers package, when compared tothe current alternatives of primary plasticizers;

7. Offer better UV resistance to the PVC compound allowing the use ofPVC compounds for longer periods or cost reduction of the UV protectionadditive packages, when compared to the current primary plasticizersalternatives;

8. Provide better physical properties at low temperatures, when comparedto the current primary plasticizers alternatives based on phthalates;

9. Provide better resistance to aliphatic solvent extraction, whencompared to current alternatives of primary plasticizers, mainlyphthalates;

In summary, the objects of this invention present complementary benefitsand additional advantages that are not foreseen by the state of the art.

The scope of this patent of invention shall not be limited to thedescribed applications, but to the terms defined in the claims and itsequivalents.

The invention claimed is:
 1. A plasticized polyvinyl chloridecomposition comprising: 100 parts by weight of at least one polyvinylchloride resin; and 1 to 200 parts by weight of a primary plasticizer,which consists of a vegetable oil, ethanol, acetic acid, and a compoundof each of formulas (I) to (VI):

wherein R is independently an epoxidized oleyloxy group, an epoxidizedlinoleoyloxy group, or an epoxidized linolenoyloxy group; and whereinthe primary plasticizer has an oxirane index of between 4 and
 8. 2. Theplasticized polyvinyl chloride composition of claim 1, wherein mono- anddi-glycerides make up less than 50 percent by weight of the primaryplasticizer.
 3. The plasticized polyvinyl chloride composition of claim1, wherein the vegetable oil has an iodine index between 120 and
 170. 4.The plasticized polyvinyl chloride composition of claim 1, wherein thevegetable oil is soybean oil.
 5. A plasticized polyvinyl chloridecomposition comprising: 100 parts by weight of at least one polyvinylchloride resin; and 1 to 200 parts by weight of a primary plasticizer,which consists of a vegetable oil, glycerin, acetic acid, and a compoundof each of formulas (I) to (V):

wherein R is independently an epoxidized oleyloxy group, an epoxidizedlinoleoyloxy group, or an epoxidized linolenoyloxy group; and whereinthe primary plasticizer has an oxirane index of between 4 and
 8. 6. Theplasticized polyvinyl chloride composition of claim 5, wherein compoundsof formulas (II) and (III) make up at least 50 percent by weight of theprimary plasticizer.
 7. The plasticized polyvinyl chloride compositionof claim 5, wherein the vegetable oil has an iodine index between 120and
 170. 8. The plasticized polyvinyl chloride composition of claim 5,wherein the vegetable oil is soybean oil.
 9. A plasticized polyvinylchloride composition comprising: 100 parts by weight of at least onepolyvinyl chloride resin; and 1 to 200 parts by weight of a primaryplasticizer, which consists of a vegetable oil, ethanol, acetic acid,and a compound of each of formulas (I) to (VI):

wherein R is independently an epoxidized linear molecular chain ofvegetable oil fatty acid ester having between 20 to 41 carbon atoms; andwherein the primary plasticizer has an oxirane index of between 4 and 8.10. The plasticized polyvinyl chloride composition of claim 9, whereineach of the epoxidized linear molecular chain of vegetable oil fattyacid ester R is independently chosen from epoxidized oleyloxy group, anepoxidized linoleoyloxy group, and an epoxidized linolenoyloxy group.11. The plasticized polyvinyl chloride composition of claim 9, whereinthe vegetable oil is soybean oil.